DOI: 10.1007/s00382-015-2888-3
Scopus记录号: 2-s2.0-84945579910
论文题名: Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current
作者: Shankar D. ; Remya R. ; Vinayachandran P.N. ; Chatterjee A. ; Behera A.
刊名: Climate Dynamics
ISSN: 9307575
出版年: 2016
卷: 47, 期: 2017-03-04 起始页码: 1049
结束页码: 1072
语种: 英语
英文关键词: Biogeochemistry
; Chlorophyll
; Eastern boundary current
; Indian Ocean
; Mixed layer
; Monsoon
; Ocean dynamics
; Turbulent mixing
英文摘要: Though the deep mixed layers (MLs) that form in the northeastern Arabian Sea (NEAS) during the winter monsoon (November–February) have been attributed to convective mixing driven by dry, cool northeasterly winds from the Indian subcontinent, data show that the deepest MLs occur in the northern NEAS and the maxima of latent-heat and net heat fluxes in the southern NEAS. We use an oceanic general circulation model to show that the deep MLs in the NEAS extend up to ~20°N till the end of December, but are restricted poleward of ~22°N (~23°N) in January (February). This progressive restriction of the deep mixed layers within the NEAS is due to poleward advection of water of lower salinity by the West India Coastal Current (WICC). The deep MLs are sustained till February in the northern NEAS because convective mixing deepens the ML before the waters of lower salinity reach this region and the wind stirring and convective overturning generate sufficient turbulent energy for the ML to maintain the depth attained in January. Though the atmospheric fluxes tend to cool the ML in the southern NEAS, this cooling is countered by the warming due to horizontal advection. Likewise, the cooling due to entrainment, which continues in the southern NEAS even as the ML shallows during January–February, is almost cancelled by the warming caused by a downwelling vertical velocity field. Therefore, the SST changes very little during December–February even as the ML shallows dramatically in the southern NEAS. These deep MLs of the NEAS also preclude a strong intraseasonal response to the intraseasonal variability in the fluxes. This role of horizontal advection implies that the ML depth in the NEAS is determined by an interplay of physical processes that are forced differently. The convective mixing depends on processes that are local to the region, but the advection is due to the WICC, whose seasonal cycle is primarily forced by remote winds. By inhibiting the formation of deep MLs in the southern NEAS, the WICC limits the region of formation of the high-salinity water masses of this region. Since the deep MLs in the NEAS have been linked to the high chlorophyll concentration there, our results imply that the conventional approach of averaging over boxes for studying the impact of physics on biogeochemistry can mask important details that are due to advection because it is the advective component of any budget that is most affected by the averaging process. © 2015, Springer-Verlag Berlin Heidelberg. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/53590
Appears in Collections: 过去全球变化的重建
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作者单位: CSIR-National Institute of Oceanography, Dona Paula, Goa, India; Academy of Scientific and Innovative Research (AcSIR), CSIR-National Institute of Oceanography, Dona Paula, Goa, India; Indian Institute of Science, Bangalore, India; ESSO-Indian National Centre for Ocean Information Services, Hyderabad, India
Recommended Citation:
Shankar D.,Remya R.,Vinayachandran P.N.,et al. Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current[J]. Climate Dynamics,2016-01-01,47(2017-03-04)